Field of Invention
The present invention relates to a center bearing bush unit for a propeller shaft. More particularly, the present invention relates to a center bearing bush unit for a propeller shaft, which can effectively decrease the amount of large/small displacement that occurs in the propeller shaft during driving of a vehicle.
Description of Related Art
In general, a rear-wheel or four-wheel drive vehicle has a propeller shaft that transmits power output from an engine up to a differential via a transmission. In a case where the length of the propeller shaft is long, the propeller shaft is formed into a two-piece structure. In the two-piece structure, a center bearing bush unit assembled with a body of the vehicle is provided at a central portion of the propeller shaft.
FIG. 1 is a configuration view showing a partial section of a center bearing bush unit for a propeller shaft according to a related art.
As shown in FIG. 1, the center bearing bush unit 20 according to the related art is mounted between a center bearing 21 and a mounting bracket 23 so as to reduce the movement of a propeller shaft 27 and to attenuate vibrations. Simultaneously, the center bearing bush unit 20 prevents friction between the center bearing 21 and the mounting bracket 23.
However, the center bearing bush unit 20 is made of a rubber material having a simple shape. Therefore, the center bearing bush unit 20 does not effectively absorb movements and vibrations of the propeller shaft 27 with respect to large and small displacements caused during driving of a vehicle.
Particularly, in a case where a large-displacement movement of the propeller shaft 27 occurs in sudden start or acceleration of the vehicle, the center bearing bush unit 20 does not effectively reduce the amount of movement of the propeller shaft 27, and hence the movement of the propeller shaft 27 is transmitted to a vehicle body as it is. Therefore, the ride comfort of the vehicle is deteriorated, and the fatigue degree of the center bearing bush unit 20 is increased, thereby deteriorating the durability of the center bearing bush unit 20.
Accordingly, Korean Patent Application Publication No. 2011-38505 has disclosed a center bearing bush unit for a propeller shaft in order to decrease large- and small-displacement movements of the propeller shaft.
In Korean Patent Application Publication No. 2011-38505, as shown in FIGS. 2 and 3, the center bearing bush unit 10 is mounted between a center bearing 7 mounted to a propeller shaft 1 and a mounting bracket 9 fixed to a vehicle body frame while surrounding the center bearing 7. The center bearing bush unit 10 is configured with a bush body 11 provided by integrally forming a projection 13, first/second modified guide grooves 15 and 17 and a rib stopper 19. One will appreciate that such integral components may be monolithically formed. Thus, the center bearing bush unit 10 decreases small- and large-displacement movements of the propeller shaft 1, caused during driving of a vehicle.
However, the center bearing bush unit 10 has a complicated shape, and therefore, the tuning of the center bearing bush unit 10 is difficult when a change in characteristic of the center bearing bush unit 10 is required due to a change in operational environment.
In addition, the durability of the first/second modified guide grooves 15 and 17 is structurally weak, and therefore, it is highly likely that cracks may occur in a test for the durability of the center bearing bush unit 10. Since upper and lower gaps A and B are identical to each other, based on FIG. 3, it is difficult to absorb the amount of displacement caused by the weight of the propeller shaft. Therefore, the vibration insulation performance is degraded due to the difference in rigidity between upper and lower portion of the center bearing bush unit.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.